1. Field of the Invention
The present invention is related to a surface texture measuring instrument. More particularly, it is related to a surface roughness measuring instrument which can be easily and directly located on a surface of an object to be measured even when measuring a large-sized object.
2. Description of the Related Art
In general, a conventional surface texture measuring instrument has a table on which the object to be measured is located. But, when the surface texture of the large-sized object that cannot be located on the table because of its size or weight is to be measured, a method of measuring the surface texture of the object is used wherein the large-sized object is cut into small pieces, to enable it to be located and measured on the table, or by replica plating, and so on. These methods are disadvantageous in that a lot of time and effort is needed to measure the surface texture of the object by using a conventional instrument. Although some of the conventional instruments can be directly located on the surface of the object without the need for the table, to increase the accuracy of the measurement, the user must adjust the pick-up to a zero-potential, which means that the longitudinal axis of the pick-up and the traversing direction of the pick-up become substantially parallel to the surface of the object, before starting the measurement. The same disadvantages as described above are incurred for the adjustment process. Additionally, the conventional instrument usually comprises a pick-up, a driving unit for driving the pick-up, a datum level plate enclosed in the driving unit, and a guide block on the datum level plate for movably supporting the pick-up; the guide block being driven by the driving unit on the surface of the datum level plate. The instrument constructed as described above is, however, relatively heavy and large, has a relatively large and heavy datum level plate, and is not easily carried and placed on an object to be measured by a user.